Distribution of the perivascular nerve Ca 2+ receptor in rat arteries

1 We recently showed that perivascular sensory nerves of mesenteric branch arteries express a receptor for extracellular Ca 2+ (CaR), and reported data indicating that this CaR mediates relaxation induced by physiologic levels of Ca 2+ . We have now tested whether the perivascular sensory nerve CaR‐linked dilator system is a local phenomenon restricted to the mesentery, or is present in other circulations. 2 Vessels from the mesenteric, renal, coronary, and cerebral circulations were studied. Immunocytochemical analysis was performed using anti‐CaR and anti‐neural cell adhesion molecule (NCAM) antibodies. Wire myography was used to assess contracation and relaxation. 3 Although perivascular nerves of all arteries stained for CaR protein, there were regional differences. A morphometric method used to estimate CaR positive nerve density revealed the following rank order: mesenteric branch artery>basilar artery=renal interlobar artery>main renal trunk artery>left anterior descending coronary artery. 4 Vessels from the mesentery, renal, coronary, and cerebral circulations showed nerve‐dependent relaxation in response to electrical field stimulation (EFS) when precontracted with serotonin in the presence of guanethidine. The degree of Ca 2+ ‐induced relaxation of mesenteric, renal, and cerebral arteries positively correlated with the magnitude of EFS‐induced relaxation. In contrast, coronary arteries contracted at Ca 2+ levels between 1.5 and 3 mmol L −1 , and relaxed to a small degree to 5 mmol L −1 Ca 2+ . 5 Thus, a functional perivascular sensory nerve CaR‐linked dilator system is present to varying degrees in the mesenteric, renal, and cerebral circulations, but only to a very limited extent in the coronary circulation.British Journal of Pharmacology (1998) 125 , 1397–1404; doi: 10.1038/sj.bjp.0702195